Elevator control system



p 1941- E. u. LASSEN ELEVATOR CONTROL SYSTEM Filed July 10, 1939 I Patented Sept. 9, 1941 ELEVATOR CONTROL SYSTEM Eivind U. Lassen, Whitefish Bay, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application July 10, 1939, Serial No. 283,542

(oust-29) 4 Claims.

This invention relates to control systems for electric elevators and the like, and is particularly applicable to means for stopping and maintaining the elevator car level with any of its several landings.

The patent to G. C. Brown, No. 1,961,133, of

- June 5, 1934, discloses an automatic leveling control system for elevators and the like having electronic control means which provides for automatic leveling of the elevator car when it is within a given distance from the landing at which it is to be stopped. In this system a single dead zone is provided at each of the landings and the elevator is stopped as the same moves into such zone. The dead zone must be relatively narrow in order to obtain accurate leveling, and in practice it has been found that unless a low and constant landing speed is em played it is difllcult to efiect stopping within the dead zone without one or more re-leveling operations.

The present invention has among its objects to provide an improved controller of the type disclosed in the aforementioned patent which is adapted for use in connection with elevators having high landing speeds and which reduces to a minimum the number of re-leveling operations required to effect stopping of the elevator car within a relatively narrow dead zone.

The accompanying drawing illustrates an embodiment of the invention which will now be described, it being understood that various modifications may be made in the embodiment illustrated without departing from the spirit and scope of the appended claims.

In the drawing,

Figure 1 is a diagrammatic view of a control system embodying the invention, and

Fig. 2 is a diagrammatic representation of certain of the operating characteristics of the control means shown in Fig. 1.

Referring to Fig. 1, the same illustrates a reversible motor M for raising and lowering an elevator car C within a hatchway having a plurality of floor landings, one of which is indicated by reference character F. Motor M may be of the squirrel cage induction type to. be supplied with current from a polyphase supply circuit indicated by lines L L and L One terminal of motor M is permanently connected to line L and a pair of normally open double pole reversing switches I and 2 are provided for selectively establishing reverse power connections between the other two terminals of said motor and lines L and IF. Each of. the switches tions indicated by reference characters U and D. I

tacts H] to I5, inclusive.

and 2 is provided with an operating winding a and a set of normally open auxiliarycontacts b and it is assumed that switch I provides for operation-of motor M in its up direction, and that switch 2 provides for operation of said motor in its down direction. Motor M is provided with a brake B which is normally set and is releasable by a winding 3 which is permanently connected across two of the terminals of motor M.

The reversing switches and 2 are selectively controlled by a car switch CS having stationary contacts 5 to 9, inclusive, and movable con- Said movable contacts are electrically connected and are mounted upon a drum which is movable in opposite directions out of an intermediate off position into posi- The car switch CS also controls a relay l6 which in turn controls a relay I1, and as hereinafter set forth said relays provide for control of a floor leveling mechanism. Relay I6 is provided with an'operati'ng winding IS, a set of normally open contacts li and a set of normally closed contacts |5, and relay H is provided with an operating winding H, a set of'normally open contacts and a set of normally closed contacts li I The leveling control mechanism includes a pair of normally open electromagnetic relays I8 and IQ for selectively establishing maintaining circuits'for reversing swit'ches and 2. Relay I 8 is provided with an operating winding I8 which is adapted to be energized from a transformer T through a tube 20 and relay I9 is provided with an operating winding I9 which isadaptedto be energized from a transformer T through a tube 2|. The tubes 20 and 2| are of the gaseous electron discharge type, and the former tube is provided with a'cathode 20", an

, anode 20 and a control grid 20, while the latter rived from a rectifier 23.

ings of transformers T and T are permanently tube is provided with a cathode 2|, an anode 2| and a control grid 2|. The cathodes 20'- and 2| may be heated'in any well known manner and the grids 2|] and 2| are subjected to control by an A. C. potential derived from a transformer 22 and also by a D. C. potential de- The primary windconnected across lines L and L and the secondary windings theroef are normally connected to the cathodes 2|! and 2| by contacts |6 of relay Hi.

Transformer 22 is mounted upon the elevator car 0 and is provided with an E-shaped core 2 member 25 having on its outer legs windings 24; -.and'2lb, respectively, and on its center leg windings 25 and 26. Mounted in'the hntch= way and coplanar with the face of core 26 are atures, 25, one of such armatures being provided for each floor landing where itis' 11 W: to obtain automatic leveling of the elevator car. when ature 25 is opposite the core 26 it reduces the reluctance of the mastic circuit of the transformer, and thus increases the electro metic coupling between coils M and 243 on the one hand, and the center coils 2 5 and it on the other hand. The coils 2d and 2d are connected in series across lines L and L and they are wound in such a manner that the dunes which they induce in the center leg ccel each other. so as to normallyproduceno resultant flux in said center leg. 0n the other hand, if an ature 25 bridges only the lower leg and the center leg of core 24! as indicated in dotted lines, a flux passes through the lower and center legs which induces a voltage of a certain'phase relation with respect to the voltage of the coils 24 and 28 in the coils 25 and 2t, whereas it the "armature 25 bridges the upper and center legs of said core a voltage is induced in the coils 2t and 2 3 which is opposite in phase to the first mentioned induced voltage.

Rectifier 23 is supplied with current from a transformer 'I which is permanently connected across lines L and L and said rectifier has a permanent resistance R and adjustable resistances RF and It connected in series across the output terminals thereof. The grid 20 of tube 20 is permanently connected to the negative outadjustable resistance R Adjustable resistance R. isnormally shunted by contacts l'l of relay 11.

As is apparent from the foregoing, the grids 20 and 2| c of tubes 20 and 2| are both subjected to'a negative grid bias by rectifier 23 which is of a given value when resistance R is shunted by contacts of relay I1 and is of an increased value upon opening of said contacts. Also it is apparent that the grid 20 or tube 20 is sub- Jected to control by the voltage induced in transtormerooil 24 and that the grid 2| of tube 2| is subjected to control by the voltage induced in Re! gfto the graph shown in Fig. 2, the

"represents the potential impressed betwee theanode and cathode of one of the tubes l assures the tube conducting when the negative grid bias is oi the value W.

The function and operation of the aforedescribed controller will now be more iully Set forth. Ii the elevator car is standing still and the operator desires to move it in a downward direction he throws the car switch CS lntoii's D position, thereby completing a circuit from line l by conductor 26, to stationary contact 5, through contacts to and E2, to stationary contact ll, through the'operating winding 2 of reversing switch 2 to line L Switch 2 thus responds and in respon 1| r the same establishes power cotions for releasingbralse B and for causing oper ation of motor lid in its down direction Also upon movement of the car switch CS into its D position relay to is energized by a circuit extending from lin L by conductor 26, to stationary contact 5, through contacts it and id, to stationary contact 8 and through the op'erat winding th of said relay to line L Relay it responds upon closure of relay to, the same being energized by a circuit extending from line, L by conductor 21, through auxiliary contacts 2" of reversing switch 2, through contacts it of relay it and through the operating winding ll to line L The contacts its of relay it are thus opened to disconnect tubes 20 and 2| from the secondary dings of transformers T and T, and also th contacts |l of relay are opened to include resistance R, between the output terminals of rectifier 23 whereby the tubes 28 and 2| are subjected to the negative grid bias E shown I in Fig. 3.

Assume that the elevator car is moving down- I wardly toward landing F. During movement of ginning vof the half cycle when the anode of said tube is positive with respect to the cathode. I! the car switch 08 is now returned to oil! position the aforedescribed energizing circuit for down reversing switch 2 is interrupted and relay I6 is also immediately deenergized to establish circuit between transformers T and 'I and the cathodes of tubes 20 and 2|. Since tube 2| is now rendered T. Relay I9 thus responds and down reversing 20 or 2| when contacts l6 of relay l6 are in closed position, and the curve i represents the control characteristic of the tube, that is the which must be impressed on the grid,

order to render the tube conducting. Also. mm; 2, ill represents the negative bias to which "thegrid of each tube is subjected when resist- R? is shunted by contacts |'I of relay l1,

. 1 and represents the negative bias to which the [grid of; each tube is subjected upon opening of said contacts. The curves E2 and Er represent grid voltages which are induced in transformer 22, the curve Ez representing the induced grid voltage which is required to render the tube conducting when the negative grid biasis' oi thevalue E and the curve Es representing switch 2 is maintained energized by a circuit extending from line L to stationary contact I through movable contacts l0 and I! to stationary contact 8 and through relay i8 and the operating winding 2 of switch 2 to line L. Upon dropping out of relay l6, relay II is maintained energized by a circuit extending from line L by conductor 2'l, through auxiliary contacts 2" of reversing switch 2, through contacts l'l of relay l1 and through the operating winding of said relay to line L.

As the elevator car moves nearer to the landing F the lower leg at transformer core 2i moves away from the armature 25 and the induced voltage in coil 24 is thus reduced. When the elevator car'is a predetermined distance above landing F the induced voltage in coil 24 is reduced to a value which renders tube 2| nonconducting and relay I8 is thus deenergized to interrupt the aforedescribed maintaining circuit for down reversing switch 2. Upon opening of reversing switch 2 motor M is deenergized and is brought to rest under the action of its associing switch 2 at such a point above the landing- F that the elevator car C is brought to rest substantially level with landing F under normal or 7 average load conditions.

Upon opening of'down reversing switch 2, the above described maintaining circuit for relay I1 is interrupted. However, relay I1 is provided with suitable means for delaying opening movement thereof until after motor M is brought to rest under the action of brake B. Upon opening of relay I! the contacts thereof close to shunt resistance R and upon shunting of resistance R the grids 20 and 2| of tubes 20 and 2| are subjected to the negative-grid bias E shown in Fig. 2.

Assume that the elevator car during downward travel is stopped short of landing F with a load lighter than the normal oraverage load. Tube 2| is now subjected to the negative grid bias E (Fig. 2) and sufilcient voltage is induced in coil 24 to again render said tube conducting for reclosure of relay l9. Thus reversing switch 2 is energized to eifect downward operation of motor M. When the elevator car moves into a position substantially level with landing F the induced voltage in coil 24 will be less than the induced voltage E1 represented in Fig. 2 whereby the tube 2| is again rendered non-conducting. Relay I9 is then deenergized and the elevator car is stopped in a position level with the land- Assume now that the load in the elevator car exceeds the normal or average load and that the car overtravels downwardly beyond the landing F. The armature 24 will be so located with respect to core 24 that the reluctance of the upper magnetic path is less than that of the lower path. Under this condition the voltage impressed on the grid 2 l at the beginning of the positive half cycle is negative but'the voltage of the grid 20 during the beginning of the same half cycle is positive. Tube 20 is now subjected to the negative grid bias E (Fig. 2) and the voltage induced in coil 24 is sufiicient to render said tube conducting. Relay It! will thus be energized Y by current from transformer T and upon response of said relay up reversing switch I is energized by a circuit extending from line L by conductor 26 to stationary contact 5, through movable contacts In and I5, tostationary contact 8, through relay l8 and through the operating winding of said reversing switch to line LP. Upon closure of reversing switch the elevator car moves upwardly and when the same is level with landing .F the induced voltage in coil 24- is reduced to a value which renders tube 20 non-conducting. Relay l8 is then deenergized and the elevator car is stopped in a position substantially level with the landing F. As is apparent, re-leveling operations by the relays l8 and I! are relatively short so that motor M irrespective of its normal speed cannot gain any appreciable velocity. The elevator car is thus brought to rest level with the landing by a single releveling operation.

Upon movement of the car switch CS into its up position, up reversing switch is energized by a circuit extending from line L to stationary contact 5, through contact segments l0 and II to stationary contact 5, and through the operating winding I of reversing switch to line L Also upon. movement of car switch CS into its U position relay I6 is energized by a circuit extending from line L by conductor 26, to'stationary contact 5, through movable contact segments l0 and [3 to stationary contact 8 and through the operating winding Hi of said relay to line L Closure of relay l6 establishes the aforedescribed energizing circuit for relay ll. Upon return of car switch CS to off position, during upward movement of the elevator car, tube 20 acts in substantially the same manner as does tube 2| during downward movement of the elevator car to deenergize motor M at a predetermined distance from landing F. Thereafter the tubes 2|! and 2| act as hereinbefore described to efiect a re-leveling operation if the elevator car over-shoots or stops short of the landing.

What I'claim as new and desire to secure by Letters Patent is:

1. An electric elevator system comprising, in combination, a control switch for effecting operation of the elevator car in opposite directions selectively, of leveling means for controlling the operation of said car when said switch is returnedto off position and the car is near a landing, said leveling means including two gaseous electron discharge tubes, one for each direction of operation of said car, each of said tubes having a grid, a transformer having relatively movable parts, one part mounted on the car and the other part located at a landing and adjacent to the path of said first part, said transformer having a primary winding connected to an alternating current source and a secondary winding arranged to have induced therein a voltage, the magnitude of which varies in accordance with the position of the car relative to said landing, means for subjecting said'grids to said varying voltage and to a biasing potential of given value upon return of said switch to off position to provide for continued operation of the car until the same moves into a predetermined zone at said landing, and means acting upon stopping of said car within said zone for subjecting said grids to said varying voltage and to a second biasing potential which provides for a leveling operation of the car upon failure of the same to stop substantially level with said landing.

2. In an electric elevator system, in combination, a control switch for effecting operation of the elevator car in opposite directions selectively, electric valve means for controlling the operation of said car when said control switch is returned to off. position and said car is near a landing, means for supplying a control voltage which varies in accordance with the position' of said car when said car approaches said landing, and means for subjecting said valve means to control bysaid varying voltage and also to control by a biasing potential of given value to render said valve means effective to continue operation of said car until the same moves into a predetermined zone at said landing, and means for reducing said biasing potential upon stopping of said car within said zone to provide for restarting of said car upon failure of the same to stop within a relatively narrow zone located within said former zone.

3. In an electric elevator system, in combination, a control switch for efiecting operation of the elevator car in opposite directions selectively, a transformer having relatively movable parts, one part being mounted upon said car and the other being located at a landing and adjacent to the path of said first part, said transformer having primary and secondary windings so arranged that a voltage is induced by the former in the latter which varies in accordance with the position of said car relative to said landing,

electric valve means for controlling the operation of said car when the same is near said landing and said control switch is returned to 0d position, means for subjecting said valve means to control by said varying voltage and also to control by a biasing potential of given value to render said valve means efiectlve to continue the operation of said car until the same moves into a predetermined zone at said landing, and means acting upon stopp of said car in said zone to modify the value of said biasing potential and thereby render said valve means efiective to provide a leveling operation of said car upon fallare of the same to stop substantially level with said landing.

4.1:: an electric elevator system. in combination, an elevator car. a motor for driving said car. a reversing controller for said motor including a control switch for establishing and interrupting hoisting and lowering power connections for said motor selectively, means for supplying acontrol voltage which varies in accordance with the position oi said car with respect to a landing, electric valve control means for controlling the operation of said car when said control switch is returned to 0d position and said car is near said landing, and means for subjecting said valve means to control by said varying voltage and also to control by a biasing potential of given value to render said valve means efiective to continue operation of said car until the same moves into a predetermined zone at said landing, and means for varying said biasing potential upon failure of said car to stop within a narrow dead zone located within said former zone to render said valve means efiective to restart said car for movement into'said latter zone.

MVIND U. LASSmI. 

